The present invention relates to truck transport apparatus, for example, for use in automobile plants for transporting vehicle bodies as placed on trucks along a specified path.
As disclosed, for example, in JP-A No. 7-25440 (1995), apparatus of the type mentioned are already known.
With reference to FIGS. 22 and 23, the conventional apparatus comprises a trolley running rail (not shown), a front trolley 301 and a rear trolley (not shown) arranged along the rail in a truck running direction, a truck body 311 connected to the front trolley 301 and the rear trolley at a lengthwise intermediate portion of each trolley so as to permit each trolley to pivotally move horizontally, a driven rod 321 having a front end connected to the front trolley 301 and a rear end connected to the rear trolley, and a pair of transport rollers (not shown) arranged respectively at opposite sides of a straight path of movement of trucks for holding the driven rod 321 therebetween from opposite sides thereof to give the rod a propelling force, the driven rod 321 being connected to the vehicle body 311.
With the conventional apparatus described, the transport rollers are provided only for the straight path of movement of trucks, and are not provided for curved path of movement. Accordingly, when the truck is to be traveled along the curved path, trucks are connected together or disconnected as desired so as to push the truck on the curved path by the following truck or trucks or to draw the truck thereon by a preceding truck or trucks.
To obviates such a troublesome procedure, it is desirable to provide transport rollers also for the curved path, whereas the following problems then need to be overcome.
When a truck is about to move into the curved path, the lengthwise intermediate portion of the driven rod moves radially inwardly of the curved path. The transport rollers are therefore shifted toward or away from the curved path. The greater the amount of shift, the greater the degree is to which the smooth travel of the truck is impaired.
Since the driven rod 321 is connected to the truck body 311 in the case of the conventional apparatus, the amount of shift of the driven rod 321 becomes inevitably great.
The conventional apparatus further includes another driven rod 331 having a front end connected to a head trolley (not shown) preceding the front trolley 301 and a rear end connected to the front end of the driven rod 321.
When the driven rod 321 following the driven rod 331 is to move past the transport rollers, the two driven rods 331, 321 make an angle xcex8 therebetween. The smaller this angle xcex8, the markedly greater the amount of shift of the transport rollers. The truck therefore fails to move past the transport rollers smoothly.
When the preceding driven rod 331 is forwarded by the transport rollers in the conventional apparatus, the following driven rod 321 is immediately advanced to the location of the transport rollers, so that the transport rollers shift abruptly greatly.
An object of the present invention is to overcome the foregoing problems and to provide a truck transport apparatus which enables trucks to travel smoothly.
The present invention provides an apparatus for transporting trucks which comprises a trolley running rail, a front trolley and a rear trolley arranged along the rail in a truck running direction, a truck body connected to the front trolley and the rear trolley at a lengthwise intermediate portion of each trolley so as to permit each trolley to pivotally move horizontally, a driven rod having a front end connected to a rear end of the front trolley so as to make the front trolley free to pivotally move horizontally and a rear end connected to a front end of the rear trolley so as to make the rear trolley free to pivotally move horizontally, and a pair of transport rollers for holding the driven rod therebetween from opposite sides thereof to give the rod a propelling force, the rail having a straight path of movement and a curved path of movement, the driven rod being extensible when the truck is about to move into the curved path from the straight path and contractable when the truck is about to move into the straight path from the curved path.
When the truck of the transport apparatus of the invention is about to advance into the curved path of movement, the front trolley and the rear trolley are horizontally moved and flexed relative to the driven rod by the extension of the rod, whereby the driven rod is positioned outwardly of a line through the lengthwise midpoints of the front and rear trolleys by an amount corresponding to the flexure of the front and rear trolleys. This means that the shift of the transport rollers in the radial direction of the curved path diminishes, permitting the truck to travel smoothly.
Preferably, the apparatus has the following feature. The rail comprises a pair of guide members extending longitudinally of the rail and opposed to each other as horizontally spaced apart by a predetermined distance, and a horizontal front guide roller and a horizontal rear guide roller are mounted respectively on front and rear portions of each of the trolleys and held between the guide members, the connection between the front trolley rear end and the driven rod front end having a pivotal center in coincidence with the center of rotation of the rear guide roller of the front trolley, the connection between the rear trolley front end and the driven rod rear end having a pivotal center in coincidence with the center of rotation of the front guide roller of the rear trolley.
When the trolleys move past the transport rollers, it is likely that the transport roller will push the approximate pivotal center of the connection sideways outward, causing the front guide roller to contact the outer guide member. Even in such a case, the trolley is unlikely to move pivotally since no principle of the lever and fulcrum works. Accordingly, there is no likelihood that the front and rear guide rollers will collide with the guide member repeatedly, hence no noise. The trolleys therefore travel with improved smoothness.
A preceding driven rod connected at a front end thereof to a head trolley preceding the front trolley has a rear end connected to a front end of the front trolley so as to make the front trolley free to pivotally move horizontally, and a following driven rod connected at a rear end thereof to a tail trolley following the rear trolley has a front end connected to a rear end of the rear trolley so as to make the rear trolley free to pivotally move horizontally, the connection between the front trolley front end and the preceding driven rod rear end having a pivotal center in coincidence with the center of rotation of the front guide roller of the front trolley, the connection between the rear trolley rear end and the following driven rod front end having a pivotal center in coincidence with the center of rotation of the rear guide roller of the rear trolley, the preceding driven rod and the following driven rod each having opposite side faces joined to respective side faces of the first-mentioned driven rod so as to be flush therewith. Like the driven rod, the preceding and following driven rods can then be smoothly moved past the transport rollers.
When the head trolley is provided at the front end thereof with a head member having a front end face with a generally V-shaped contour in horizontal section, the head member mitigates the impact to be produced when the head trolley advances into contact with the transport rollers.
When comprising a telescopic pipe, the first-mentioned driven rod can be extended or contracted by a simple structure.
The rail has a curved path of movement, and the pair of transport rollers are arranged on opposite sides of the curved path and supported by a horizontal pivotal body so as to be movable together. This enables the truck to travel the curved path by itself.
The pair of transport rollers are a drive roller positioned on one side of the curved path and a holding roller positioned on the other side thereof, and the pivotal body comprises a main pivotal arm having the drive roller mounted on a forward end thereof, a support arm fixed at a base end thereof to a lengthwise intermediate portion of the main pivotal arm and extending across the curved path therebelow, and a driven pivotal arm carrying the holding roller at a forward end thereof and pivoted at a base end thereof to a free end of the support arm so as to be horizontally movable relative to the support arm.
A vertical outer square pipe is secured to a base end of the main pivotal arm, and a vertical inner square pipe is fitted in the outer square pipe so as to be horizontally movable, the outer pipe being packed with an elastic material around the inner pipe so that the diagonals of one of the pipes are displaced from those of the other pipe by 45 degrees. An elastic force for pressing the drive roller against the rail can then be given to the main pivotal arm by a simple arrangement.
Preferably, a spring is attached to and extends between the support arm and the driven pivotal arm for biasing the driven arm in a direction to move the holding roller toward the drive roller.
Furthermore, other truck transport apparatus are defined in appended claims 10 to 18. Use of the structures thus claimed enables the truck to travel the curved path by itself, with the driven rod not necessarily extended or contracted.